Cellular Respiration: Glucose Breakdown and Energy Production – PDF

Ch. 8 Cellular Respiration Cellular respiration is a cellular process that breaks down nutrient molecules with the concomitant production of ATP Consumes oxygen and produces carbon dioxide (CO2) – Cellular respiration is an aerobic process. Usually involves the breakdown of glucose to CO...

Ch. 8 Cellular Respiration Cellular respiration is a cellular process that breaks down nutrient molecules with the concomitant production of ATP Consumes oxygen and produces carbon dioxide (CO2) – Cellular respiration is an aerobic process. Usually involves the breakdown of glucose to CO2 and H2O – Energy is extracted from the glucose molecule: Released step-wise Allows ATP to be produced efficiently – Oxidation-reduction enzymes include NAD+ and FAD as coenzymes 1  6.4 Oxidation-Reduction Reactions and Metabolism Oxidation-reduction (redox) reactions: Electrons pass from one molecule to another. Oxidation – loss of an electron. Reduction – gain of an electron. Both take place at the same time. One molecule (or atom) accepts the electron given up by the other. Example: In the production of NaCl, sodium is oxidized and chlorine is reduced; OIL RIG (oxidation is loss, reduction is gain). 2  NAD+ and FAD NAD+ (nicotinamide adenine dinucleotide) As a coenzyme of oxidation-reduction, it is: Oxidized when it gives up electrons. Reduced when it accepts electrons. Each NAD+ molecule is used over and over again. FAD (flavin adenine dinucleotide) Also a coenzyme of oxidation-reduction. Sometimes used instead of NAD+. Accepts two electrons and two hydrogen ions (H + ) to become FADH2. 3 Overall Equation for Aerobic Cellular Respiration  Phases of Cellular Respiration 1 Cellular respiration includes four phases: Glycolysis is the breakdown of glucose into two molecules of pyruvate. It occurs in the cytoplasm. ATP is formed. It does not utilize oxygen (anaerobic). Preparatory (prep) reaction Both molecules of pyruvate are oxidized and enter the matrix of the mitochondria. Electron energy is stored in NADH. Two carbons are released as CO2 (one from each pyruvate). 5  Phases of Cellular Respiration 2 Citric acid cycle Occurs in the matrix of the mitochondrion and produces NADH and FADH2. A series of reactions, releases 4 carbons as CO2. Turns twice per glucose molecule (once for each pyruvate). Produces two immediate ATP molecules per glucose molecule. Electron transport chain (ETC) A series of carriers on the cristae of the mitochondria. Extracts energy from NADH and FADH2. Passes electrons from higher to lower energy states. Produces 32 or 34 molecules of ATP by chemiosmosis. 6 Mitochondrion Structure and Function Figure 8.7 Access the text alternative for slide images. (photo): Keith R. Porter/Science Source 7 Overview of Aerobic Respiration 1 Figure 8.9 Access the text alternative for slide images. 8 Cellular Respiration Figure 8.1 Access the text alternative for slide images. (photo): Schlegelfotos/Shutterstock 9  The Breakdown of Glucose Figure 8.2 Electrons are removed from substrates and received by oxygen, which combines with H + to become water. Glucose is oxidized and O2 is reduced. 10  Phases of Cellular Respiration 1 Cellular respiration includes four phases: Glycolysis is the breakdown of glucose into two molecules of pyruvate. It occurs in the cytoplasm. ATP is formed. It does not utilize oxygen (anaerobic). Preparatory (prep) reaction Both molecules of pyruvate are oxidized and enter the matrix of the mitochondria. Electron energy is stored in NADH. Two carbons are released as CO2 (one from each pyruvate). 11  Phases of Cellular Respiration 2 Citric acid cycle Occurs in the matrix of the mitochondrion and produces NADH and FADH2. A series of reactions, releases 4 carbons as CO2. Turns twice per glucose molecule (once for each pyruvate). Produces two immediate ATP molecules per glucose molecule. Electron transport chain (ETC) A series of carriers on the cristae of the mitochondria. Extracts energy from NADH and FADH2. Passes electrons from higher to lower energy states. Produces 32 or 34 molecules of ATP by chemiosmosis. 12  Phases of Cellular Respiration 2 Citric acid cycle Occurs in the matrix of the mitochondrion and produces NADH and FADH2. A series of reactions, releases 4 carbons as CO2. Turns twice per glucose molecule (once for each pyruvate). Produces two immediate ATP molecules per glucose molecule. Electron transport chain (ETC) A series of carriers on the cristae of the mitochondria. Extracts energy from NADH and FADH2. Passes electrons from higher to lower energy states. Produces 32 or 34 molecules of ATP by chemiosmosis. 13 Phase 1 Glycolysis Phase 2 preparatory reaction Phase 3 Citric Acid Cycle Phase 4 Electron Transport Chain/Chemiosmosis  Chemiosmosis High H+ concentration H+ H+ H+ pump in electron H+ transport chain H+ H+ ATP ADP + P ATP ADP + P synthase NADH NAD + H+ complex ATP H+ Low H+ concentration 18 Electron Transport Chain Figure 8.10 19  Electron Transport Chain Location: Cristae – mitochondria. Aerobic prokaryotes – plasma membrane. Series of carrier molecules: Pass energy-rich electrons successively from one to another. Complex arrays of protein and cytochrome. Proteins with heme groups with central iron atoms. The electron transport chain: Receives electrons from NADH and FADH2. Produces ATP by oxidative phosphorylation. Oxygen final electron acceptor: Combines with hydrogen ions to form water. 20  Chemiosmosis and The Electron Transport Chain The electron transport chain complexes pump H + from the matrix into the intermembrane space of the mitochondrion. H + therefore becomes more concentrated in the intermembrane space, creating an electrochemical gradient. ATP synthase allows H + to flow down its gradient. The flow of H + drives the synthesis of ATP from ADP and inorganic phosphate by ATP synthase. Process is called chemiosmosis: ATP production is linked to the establishment of the H + gradient. ATP moves out of mitochondria and is used for cellular work. It can be broken down to ADP and inorganic phosphate. These molecules are returned to the mitochondria for more ATP production. 21  Accounting Energy Yield per Glucose Molecule Breakdown 4 Figure 8.11 Access the text alternative for slide images. 22 What happens when no O2 gas is available? Pyruvate is a pivotal molecule in cellular respiration If O2 is not available to the cell, fermentation, an anaerobic process, occurs in the cytoplasm. – During fermentation, glucose is incompletely metabolized to lactic acid, or to CO2 and alcohol (depending on the organism). If O2 is available to the cell, pyruvate enters the mitochondria for aerobic respiration. 23  Fermentation Process Fermentation is an anaerobic process that reduces pyruvate to either lactate or alcohol and CO2. NADH transfers its electrons to pyruvate. Alcoholic fermentation, carried out by yeasts, produces carbon dioxide and ethyl alcohol. Used in the production of alcoholic spirits and breads. Lactic acid fermentation, carried out by certain bacteria and fungi, produces lactic acid (lactate). Used commercially in the production of cheese, yogurt, and sauerkraut. Other bacteria produce chemicals anaerobically, including isopropanol, butyric acid, propionic acid, and acetic acid. 24 Fermentation Figure 8.6 Access the text alternative for slide images. 25 Inputs and Outputs of Fermentation Access the text alternative for slide images. 26  Advantages and Disadvantages of Fermentation Advantages: Provides a quick burst of ATP energy for muscular activity. When muscles are working vigorously for a short period of time, lactic acid fermentation provides ATP. Disadvantages: Lactate and alcohol are toxic to cells. Lactate changes pH and causes muscles to fatigue. Oxygen debt. Yeast die from the alcohol they produce by fermentation. Efficiency of Fermentation: Two ATP produced per glucose of molecule during fermentation is equivalent to 14.6 kilocalories. Complete oxidation of glucose can yield 686 kilocalories. Efficiency is 2.1% of total possible for glucose breakdown. Only 2 ATP per glucose are produced, compared to 36 or 38 ATP molecules per glucose produced by cellular respiration. 27 Photosynthesis and Cellular Respiration 28 Photosynthesis Versus Cellular Respiration Figure 8.13 Access the text alternative for slide images. 29